Overhead load supporting structure and method

ABSTRACT

A crane structure comprising a trolley, a beam member which is suspended from the trolley by flexible cables, a hoist on the trolley for changing the elevation of the beam, and a pair of hook assemblies. The beam is constructed to provide cam portions adjacent bearing seats so that the hook assemblies are guided from one bearing seat to another when the beam is lowered until the weight of the hook assembly is supported by a surface beneath them. A hook assembly stabilizing mechanism is also provided. The disclosure also includes a novel laminated hook construction which establishes line contact with a support which line forms a pivot axis for hook adjustment.

United/States Patent 11 1 Hough [5 1 OVERHEAD LfoAD SUPPORTINGSTRUCTUREAND METHOD [75] Inventor: J. Leonard Hough, Canton, Ohio [73]Assignee: Republic Steel Corporation, 1

Cleve1and,'0hio 221- Filedz Apr. 24, 1968 21 Appl.No.:723,792

' [52] US. Cl. 294/81 R, 212/11, 212/128 [51] Int. Cl. B66c 1/16 [58]Field of Search 294/81, 67, 82, 116, 94, 294/106,ll0;212/11, 128,125,130

[56] References Cited 7 .UNITE1) STATES PATENTS I 1,875,730 9/1932'Hively... 212/130 3,111,228 11/1963 Anderson..'. 3,408,034 10/1968 Lau294/116. FOREIGN PATENTS OR APPLICATIONS 416,695 7/1925 Germany 294/81224,400 11/1924 Great Britain" 294/81 1451 9 Apr. 9, 1974 1,041,3889/1966 Great Britain 294/81 Primary Examiner-Evon C. Blunk AssistantExaminer-Johnny D. Cherry Attorney, Agent, or FirmWatts, I-Ioffmann,Fisher 81. Heinke, Co.

[5 7] ABSTRACT A crane structure comprising a trolley, a beam tnem herwhich is suspended from the trolley by flexible cables, a hoist on thetrolley for changing the elevation of the beam, and a pair of hookassemblies. The beam is constructed to provide cam portions adjacentbearing seats so that the hook assemblies are guided from one bearingseat to another when the beam is lowered until the weight of the hookassembly is supported by a surfacebeneath them. A hook assemblystabilizing mechanism is also provided. The disclosure also in? cludes anovel laminated hook construction which establishes line contact with asupport which line forms a pivot axis for/hook adjustment. 7

17 Claims, 8 Drawing Figures PATENTEBAPR 9 i974,

SHEET 1 OF 2 FIGS ' INVENTOR. J. LEONARD HOUGH BY Waii'5,{offmann:fishmi-{einkm FIGZ ATTORN E YS.

PATENTEDAPR 919m 3802.730

SHEET 2 BF 2 l I l I so 1 l rsl \l 6| 6o V a 63 A 64 (WIDE l(INTERMEDIATE (INTERMEDIATE rNARROW 90 91 L rMl NlMUM F 0c 96 95 I00 94lol f (INTERMEDIATE -WIDE 1 (INTERMEDIATE NARROW FNVENTOR. H66 J LEONARDHOUGH OVERHEAD LOA SUPPORTING STRUCTURE "AND METHOD BACKGROUND OF THEINVENTION 1. The Field of the Invention The invention relates to anoverhead load supporting structure and more particularly relates toaload supportingstructure having load engaging hooks or grabs which aremanipulated to engage a-load and transport the load from place to placewithin a building structure or the like. 1

Overhead load supporting structures such as cranes equipped with loadengaging hooks are often utilized in steel mills or similar plants totransport ladies for molten metal. Such ladles. are generallyconstructed with trunions extending from diametrically opposed locationson the ladle. Thetrunions are engaged by the hooks for transport.

Generally, support structures for transporting ladles of the typereferred to include an overhead trolley movable alongtracks, a hoistmechanism, and a hanger In many instances ladles of differentdiametrical dimensions are utilized in the same steel mill. Accordinglycrane structures of the type referred to must be equipped to transportladles having various dimensions between the trunions. Since thesupporting structures carrying the hooks are commonly rigid inconstruction, shifting the position of the hook structures relative tothe hanger beam to accommodate the variouslydimensioned ladles has beena problem.

2. THE PRlOR ART Proposals have been madefor the use of power drivenshifting-mechanisms for moving the load supporting structures relativeto the beam. Such proposedmechanisms are powered by electrical,hydraulic, or pneumatic motors integral with the hanger beam whichgenerally utilize a suitable system of gears, levers, or cables to shiftthe hooks. The use of such power driven shifters has not been entirelysatisfactory due to excessive shock forces which are transmitted to theelements of the drive train from the hooks. Moreover, the drive trainsare, during use in ladle transport, subjected to extremely high ambienttemperatures. Both the exposure to high temperature and the attendantlarge variation in ambient temperatures are factors which make the drivetrain susceptible to failure. Furthermore, flexible hoses or wiringthrough which power is supplied to the shifting mechanisms have beensubjected to fouling during operation of the crane and to deteriorationfrom the intenseheat of the environment.

The prior art has also proposed to shift hooks of a crane structure ofthe type referred to without the use of motors integral with the hangerbeams. Such proposals retained the hook shifting mechanism on the hangerbeam and employed an auxiliary hoist to operate the 2 hook shiftingmechanism. The auxiliary hoist engaged a lever or cable of the shiftingmechanism and raised the lever or cable to shift the hooks.

Less complex proposals suggested manipulating the hanger beam until theload engaging hooks were touched down. In practicing these proposals onehook was shifted toward or away from the other hook by a series ofoperations of the hanger beam during which the beam was lowered and thenshifted laterally. The other hookwas then shifted in the same manner. Insome proposals of the last mentioned type the hook structure wassupported by a cam track-formed in the hanger beam so that as the hangerbeam was moved with a hook touched down, the hook structure followed thecam track.

While less complex, these latter proposals have not been fullysatisfactory. With these less complex proposals the operator, inpractice, lowers the hanger beam until one book is supported by asurface elevated from th'efloor. If there is slight overtravel as thehanger beam is lowered, the weight of the hanger beam will be supportedby the 5 rigid hook structure. When the hanger'is so supported thehanger beam cables are relieved of their load and go slack. The cables,when slackened, often become disengaged from the sheaves about whichthey are trained. Retraining the cables in such circumstances can beextremely time consuming.

In cases where the hanger beam is to be manipulated with the loadengaging hooks touched down on a horizontal surface, the operator of thecrane is oftentimes unable to determine when the weight of the hangerbeam is being supported by the hooks. In many instances the only waythat a crane operator can determine that the hanger beam is beingsupported by a hook is by visually determining that the cables are.slack. This procedure is not desirable since any slackening of thecables risks disengaging them from the sheaves. The use of suchproposalshas therefore required, highly skillful crane operators, and resulted inrelatively slow shifting of the hooks. Even so,disentraining the cablesfrom their sheaves is common.

While it is apparent thatretaining crane cables con sumes otherwiseusable time, the time required to shift hooks on cranes is importantbecause of the great de mand for crane service on the floor of a plantsuch as a steel mill. Thus quick and reliable hook shifting is necessaryfor efficient operation throughout the plant.

Typically the hooks are rounded at their lower ends in a plane which istransverse to the. trunions. When a hook is shifted this curved surfaceengages the support in line contact along a line that parallels thetrunion axis. This contact causes difficulties because the line ofcontact is parallel to the direction. of shifting along the hangerbeamJAs a result, the hooks tend to resist tilting. When the books dotilt, the contact between the hook and horizontal surface is essentiallypoint contact as the curved edge of the hook engages the horizontalsurface. Because of the point contact, the hooks tend to twist abouttheir longitudinal axes and may tilt in a direction transverse to thedesired tilLSuch twisting and tilting has necessitated the provision ofnarrow cam tracks in the hanger beam for receiving a pin or shaft on thehook structure so that skewing of the hook structure is minimized. Theprovision of narrow cam tracks has further increased the susceptibilityof the ca SUMMARY OF THE INVENTION In accordance with the presentinvention a load supporting structure of the type referred to isprovided with a hanger beam which carries spaced hook assemblies eachcomposed of a hook and support structure. The hanger has spaced bearingseats engageable' by bearing members which form a part of the hooksupports. The hook assemblies are simultaneously shiftable, in a simpleand reliable manner, between the spaced bearing seats without need ofbook shifting mechanisms. Manipulation of the hanger beam is' suchthat'shifting the hook assemblies between alternate bearing seatsisreliably accomplished by simultaneously touching the hooks downwithout slackening the cables. More specifically the hook assemblies areI constrained for freely rotating about the lower end of the hooks asthe assemblies are shifted between the bearing seats. This is to saythat the beam is constructed so that shifting of the hooks occurswithout interference between the hook assemblies and portions of thebeam during at least a part of the shifting motion of the hook assembly.

In a preferred embodiment cam surfaces are provided on the hanger beamwhich are constructed and arranged toguide the hook assemblies towardand away from the bearing seats during the initial and terminal portionsof shifting. The hook assemblies tip and rotate freely between the camsurfaces during the remainder of the shifting movement. The camsurfacesare spaced apart so that an operator of the crane can visually determinewhen shifting of the hook support has been accomplished. Th us, shiftingthe hook support is accomplished without supporting the weight of thehanger beam upon the hook assemblies at any time, insuring that thecables are not disengaged from their the crane.

transmit substantial vertical forces during shiftingof the hook. Thusimmediate stopping of the downward movement of the beam after the hookassemblies shift transverse to the direction in whichthe bearing part isshifted relative to the hanger beam. Thus the hook as- I sembly isconstrained from tipping about the line of In the, preferred form of theinventiona pair of hook beam. Each opening defines spaced bearing seatsand cam portions adjacent the bearing-seats. A bearing part of thecorresponding hook engages a selected one of the spaced bearing seats onthe hanger beam for suspending a load from that seat. 1 I

If it is desired to shift the hook assemblies between their respectivebearing seats, the hanger beam is lowered until the hooks are toucheddown. The hanger beam continues to be moved vertically downwardlyrelative to the bearing part of each assembly. The vertical relativemovement urges the bearing part of each assembly along a cam surfaceadjacent the bearing seat. The cam-surface guides the bearing part fromthe seat and after a predetermined amount of downward movement of thehanger beam the hook assembly is tipped. This causes the bearing part ofthe hook support to fall away from the cam surface and into engagementwith a second cam surface adjacent the other bearing seat.

Tipping of the hook assemblies is pronounced and an operator of thecrane can thus visually determine when the assembly has tipped. Thedownward movement of the hanger beam is then terminatedl Each opening inthe beam provides a substantial clearance between the bearing part andany surface of the beam which could contact of the hook or grab with thesupport surface.

The cam portions of the hanger beam are disposed so that tipping of thehook assembly and attendant transfer of bearing part contact from onecam portion to the other cam occurs at a time when the bearing part isspaced substantially from any surface of the hanger beam capable oftransmitting substantial vertical forces. Accordingly, exertion ofvertical forces upon the hanger beam by-the hook assemblies is avoidedand the possibility of disengagement of the cables with the sheavesminimized. a

The hanger beam and bearing parts are interconnected by stabilizer linksengaged with the bearing parts and the hangerbeam. The connectionbetween the stabilizer links and a bearing part of the hook assemblyprevents a relative rotation between the stabilizer links and bearingpart. The connection between the stabilizer link and hanger beam affordsrelative rotation therebetween as well as sliding movement of thestabilizer link relative to the hanger beam. A stabilizer linkconstructed as described prevents skewing of the bearing part relativeto the hanger beam which might otherwise occur yet permits unrestrictedtipping of the hook assemblies about the lower end of the hook.

Where the hanger beam is constructed to support loads exerting aresultant force which is not centered on the span of the hanger beam,thehook assemblies may be shifted between multiple positions fortransporting different sized loads. In one embodiment of the invention,in which each hook assembly has only two positions, four differentdistances between the hooks are selectively available. j

A principal object of the present invention is the provision of a newand improved overhead load supporting structure wherein hook assembliescan be simultaneously shifted relative to a hanger beam of the cranequickly and without disengaging cables supporting the hanger beam fromtheir sheaves.

Other objects and advantages of the present invention are apparent fromthe following detailed description thereof made with reference to theaccompanying drawings which form a part of the specification.

DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevational view of a loadsupporting structure embodying the present invention;

FIG. 2 is a sectional view of a portion of the structure of FIG. Iviewed approximately from the plane of line 2-2 of FIG. 1' and shown ona scale which is larger than the scale of FIG. 1;

FIG. 3 is an enlarged view approximately from the plane of the line 3-3of FIG. 2;

FIG. 4 is-a fragmentary elevational view seen from the plane of the line4-4 of FIG. 1; 2

FIG. 5 is an enlarged view as seen from the plane of theline 5-5 of FIG4; I

FIG. 6 is an elevational view of a part of the structure of FIG. 1 inone operative condition; and FIGS. 7 and 8'are fragmentary views ofmodified load supporting structures embodying the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT A crane structure 10 embodyingthe present invention is illustrated in FIG. 1. The crane structure 10includes a trolley T, hanger beam B and a hoist mechanism H. The trolleyT is movable along tracks 11, 12 which are supported at elevatedlocations relative to a floor 13, or other' horizontal surface. Thetrolley T is provided with wheels 14, only a pair of which areillustrated, which permit the trolley T to be propelled along the tracks11, 12 by a suitable prime mover .(not shown). The tracks 11, 12 arealso movable as a unit transversely of their extent and since thestructure for moving the tracks may be of any one of a number ofconventional constructions it is not illustrated or described. Theillustrated embodiment of the overhead construction is merelyillustrative and may in fact merely comprise a trolley on fixed trackssince the invention can be practiced without the hanger beam B. I

The hanger-beam B is suspended from the trolley T by cables 15, 16. Thecables 15, 16 are disposed about sheaves 20, 21 connected to the beam Band extend betweentthe sheaves 20, 21 and the hoist H. The hoist H isoperative to effect vertical movement of the beam B relative to thetrolley T with the cables 15, 16 being trainedaround the sheaves toprovide a-mechanical advantage in moving the beam B. i

.The beam B is comprised of three plates 22-24 (FIG.

2) which are rigidly fixed together in spaced relation to' 27whichsupport load supporting hook assemblies 30,

31 respectively.

The hook assemblies 30, 31 are identical in construction and accordinglyonly the assembly 31 is described in detail in reference to itsconstruction and mode of operation with respect to the beam B. Thehookassembly 31 includes a hook support structure 33 which is engagedwith the end 27 of the beam B and a'load engaging grab or hook 34. Thehook support 33 includes a clevice pin 35 which supports the hook 34.The hook 34 is pivoted in a plane transverse to the beam B about theclevice pin 35. The hook 34 is constructed of steel laminations eachshaped to define a load engaging portion 36 engageable with ladletrunions as well as other loads.

The hook support 33 includes a bearing part in the form of a pin 40which suspends the support from the beam' B. The pin 40 is engaged witha suitable bearing seat on the beam B, which seat is' described ingreater detail presently. The hook support 33 additionally includesbushings 41, 42 surrounding the bearing pin 40. The bushings 41, 42 areintegrally connected to side walls 44 of the support 33. The bushingsare also con nected to vertically extending walls 45, and-ahorizonlateral movement of tally disposed w all The walls 45, 46 alsoform portions of the support and they extend transversely between theside walls 44 at spaced locations in the support. The walls 45 supportthe bushings 41, 42 at their upper ends and are connected to the wall 46at their lower ends. I

The side walls 44 of the support 33 extend downwardly from the wallmembers 45 and are apertured to receive and support the clevice pin 35.Journals 50 are disposed around the pin 35 and between the walls 44 andan eye 51 of the hook 34.

The bearing pin 40 is a generally cylindrical, shaftlike member whichextends through aligned generally triangular openings, 55b--57b in theplates 22-24, re spectively at the end 27. The openings 55b57b areidentical in configuration and function and accordingly, only'theopening 57b in the plate 24 is described. The opening 57b includes anarc'uately curved base surface 60 and converging side surfaces 61, 62extending from the base 60. The base surface 60 is transversely curvedadjacent its junctures with the sides 61,62 to define bearing seats 63,64 which are engaged selectively and one at a time, with the bearing pin40. Thus, the hook assembly 31 may be suspended from the beam B byengagement of the bearing pin 40 with a selected one of the seats 63,64. The side surfaces 61, 62 extend from the seats 63, 64 to an apex 65of the opening 57b formed by a' gently curving juncture between thesides 61, 62.

In accordance with the present invention the hook assembly 31 isshiftable between a position wherein the bearing pin 40 engages the seat64 and a position wherein the pin 40 engages the seat 63. The change inposition of the assembly 31 relative to the beam B is illustrated inbroken lines in FIG. ll. I

seat 64 to the seat 63, the beam [8 is lowered relative to the trolleyT'by operation of the hoist H until the hook 36.touches the floor 13.Further lowering of the beam B results in the bearing pin 40 movingupwardly with respect to the beam B so that the bearing pin. 40is'guided along the side of the openings 55b-57b. The sides 61, 62 ofthe openings Ssh-57b thus define a cam portion of the beam which isdefined by three spaced cam surfaces on the plates 22, 23, 24. The camportion guides the bearing pin 40 asthe beam B moves downwardly relativeto the member 31. The cam portion thus constrains the bearing pin 40 formovement in a longitudinal direction with respect to the descendingbeam.

When the beam B has .been lowered to a position at which the bearing pin40 is approximately at the location on the cam surface 62, the bearingpin 40 has been guided laterally, relative to the hook portion 36, asufficient distance to unbalance the assembly 31. The force of gravitytips the assembly 31 out of engagement with the cam surface 62 and theassembly 31 falls or is tipped so that the bearing pin 40 moves from thecam surface 62 across the opening 57 and into engagement with the camsurface 61. I

During the tipping action described, the assembly 31 rotates freelyabout the line ofengagement between the hook portion 36 and floor 13 sothat the bearing pin 40 strikes the cam surface 61 at a location 71having a slightly lower elevation than the location 70 on the camsurface 62. The rotation of the assembly 31 occurs through a largeenough angle so that an operator of the crane can visually determinewhen the bearing pin 40 is in engagement with the cam surface 61. Uponvisually determining that the assembly 31 has shifted, the craneoperator actuates' the hoist H to elevate the beam B relative to thefloor 13. The cam surface 61 moves upwardly relative to the bearing pin40 and the surfaces 60, 61 coact to guide the bearing pin 40 intoengagement with the seat 63. Continued upward movement of the beam Bresults in rotation of the hook assembly 31 about the bearing pin. 40until the assembly depends vertically from the seat 63 in its verticalbroken line position (see FIG. 1).

It should be apparent that the apex 65 of the opening 57b is spaced arelatively substantial distance from the bearing pin 40 at all timesduring shifting of the bearing configuration of the apex 65 is tominimize stress concentrationsin the plates 22-24 of the beam B underload. The base surface 60 of the opening 57 is recurved to providegenerally cylindrical bearing seats at its junctures with the sides 61,62. In the preferred operation as depicted in FIG. 3 the base surface 60does not participate in camming the pin 40 between its positions andthus pin wear is avoided The gently curving base surface 60 is soconfigured to reduce stressconcentrations around the opening 57b but mayassist in camming the pin 40 against the seat 63 if the beam B is raisedvery rapidly.

The foregoing description of the operation of the crane in shifting theassembly 31 also applies to shiftingthe'bearing pin 40 of the assembly30 in the openings'55a-57a at the end of the beam B. As illustrated-inFIG. 1, while the assembly 31'is being shifted toward the assembly 30,in the manner described, the assembly is simultaneously shifted towardthe assembly 31 in a mirror image manner. Accordingly, a detaileddescription of shifting the assembly 30 would be superfluous and isomitted.

Similarly, the operation for shifting the hook assemblies 30, 31 fromtheir vertical phantom positions of FIG. 1 to their solid line positionsis identical except that the assemblies tip in opposite directions.

THE HOOK CONSTRUCTION The hook portion 36 is constructed to provide arelatively narrow substantial line contact with the floor 13 in adirection transverse to the beam B. As illustrated in'FlGS. 4 and 5 thehook 34 is formed by a plurality of laminations of sheet steel with thelaminations in the central portion of the hooks extending intoengagement with the floor 13. The outer laminations terminate short ofthe floor 13 when the hook is touched down. Thus when a hook is touched'down, contact with the floor is established along a line transverse tothe beam B, inhibiting tipping of any part of the assembly 31transversely of the beam but readily permitting tipping I THESTABILIZING MECHANISM The assembly 31 is susceptible to pivoting ortwisting about the longitudinal axis of the member even though linecontact is established between the hook and floor as noted. Suchpivoting tends to occur when the bearing pin 40 is being shifted andparticularly if the hanger beam is swinging. Twisting of the assembly 31could result in skewing of the bearing pin 40 relative to the cams andseatsof the openings 55-57, resulting delays in shifting the hooks.

To avoid this problem the crane structure of the present invention isequipped with stabilizing mechanisms for preventing skewing of thebearing pins 40 relative 'to'the cam surfaces and bearing seats definedby the openings 55-57. In the preferred embodiment each stabilizingstructure includes a link connectedbetween the bearing pin 40 of eachassembly 30, 31 and the plates 22-24 of the beam B. The stabilizers areidentical inconstruction and accordingly only the stabilizers.associated with the plates 22, 24 and the assembly 31 are described indetail. The links 80 each include a square opening 81 adjacent one endand an elongatedslot 82 at the opposite end. Each slot 82 receives aguide pin 83 fixed to the adjacent one of the plates 22, 24. Coaction ofeach guide pin and its associated slot permits rotational as well astranslational movement of the link 80 relative to the beam B.

The bearing pin 40 includes reduced end portions 84 at each of its endswhich are square in cross-section and are snugly-received in theopenings 81 to fix the bearing pin 40 and links 80 against rotationrelative to each other. The ends 84 of the bearing pins 40 are providedwith threaded holes. A plate-like retainer member 85 is secured to theends 84 by screws 86 which extend through the retainer 85 and into theholes (FIG. 2).

The links 80 are connected at the ends of each bearing pin 40 (FIG. 2)in the manner described, so that as the bearing pin 40 is moved relativeto the openings 55b-57b the links '80 slide and rotate with respect tothe pins 83. Should the bearing pin 40 tend to skew relative to thecams, i.e. when the bearing pin 40 tends to assume a position in whichits axis is not transverse to the beam B, the ends 84 of the pin 40exert forces on the links 80 tending to rotate the link about thelongitudinal axis of the bearing pins. Due to the pin and slotconnection between the links 80 and the beam B, any tendency forrotation of the links 80 about points other than the axis of theguidepins 83 is strongly resisted by the engagement of the sides of theslots 82 with the guide pins. Thus the links 80 must rotate in unisonand accordingly lock the pins against skewing.

It will be appreciated from the foregoing description that therotational and translational pin movement permitted by the stabilizersis such that the hook assemblies can rotate freely about the lower endof the hook during tipping. Furthermore the links 80 freely permit suchtipping regardless of the vertical length of the hook assemblies.

openings 55-57 in ends of the beam B permit simultastress concentrationsaround the neous shifting of the hook assemblies 31 between a wideposition and a narrow position. The hooks thus engage loads havingdiametrical extents'which dif fer by an amount equal to the sum ofthedistances betweenthe seats 63, 64 of the openings 5557 at each end ofthe beam B.

Where the crane structure 10 is designed to permit eccentric loading ofthe beam B (i.e. where the beam B, supports a load having a resultantacting on a location of the beam B which is not equidistant between thesheaves 20, 21), an intermediate hook position can be provided byshifting only-one of the assemblies 30, or 31. The intermediate positionprovides a distance between the hooks which is intermediate the wide andnarrow positions referred to by an amount equal to the distance Dbetween the seats 63, 64 of the openings 55 57, at one end of thebeam(see FIG. 7).

As seen in FIG. 6, positioning of the members 30, 31

at the intermediate position is accomplished by providing a suitableelevated surface 13a beneath a selected assembly, the assembly. 3l'asshown, and lowering the beam B until the hook 34 touches down on thesurface 13a. The beam B continues to move downwardly until the assembly31 is shifted from the seat 64 to the cam 61. Then the beam B is againraised so that the assembly 31 is suspended from the seat 63, asillustrated in broken lines in FIG. 6. It is to be noted that thesurface 13a is elevated a sufficient distance above the floor 13 toinsure that the hook of the assembly 30 does not touch down on the floorduring shifting of the assembly 31. Thus the assembly 30 is maintainedin its FIG. 6 position during shifting of the assembly. It is alsoapparent that the assembly 30 can be individually shifted in the mannerdescribed utilizing the elevated surface 130. FIG. 7 is illustrative ofthe possible positions at which the assemblies 30, 31 may be supportedrelative to the beam B. FIG. 7 additionally illustrates a modifiedconstruction of the openings 55-57 in the beam B wherein the apexes 65of the openings are defined by slot-like recesses 65a. The upper ends ofthe recess 65a are defined by a generally circularly curved surface sothat openings are minimized.

The recesses 65a are constructed to provide substantial clearancebetween the apexes of the openings 55-57 and the path followed by thebearing pins 40 during shifting between the seats 63, 64. This construc-3,8O2,73O- I The opening 90 is a generally triangular opening having acurvilinear base94 and sides 95, 96 which are joined by a smoothlycurved apex 97. The junctures between the base 94 and sides '95, 96 arecircularly curved to define seats 100, 101 for the bearing pin 40. Theseats 100, 101 have a center line distance D-l-X therebetween. The sides95, 96 of the opening 90 converge proceeding upwardly with each of thesides defining an angle alpha, with respect to horizontal.

The opening 91 includes a base surface 104 and sides 105, 106 which areinterconnected at the apex 107 of the opening 91 by a smoothly curvingsurface. The junctures of the sides 105, 106, respectively and the base104 define circularly curved seats 1 10, 1 11 having a center linedistance D-X therebetween. It is apparent that the triangular openings90, 911 are not similar and the sides.105, 106 of the opening 91converge proceeding upwardly at an angle, beta, with respect tohorizon-.

tal and which angle is substantially larger than the angle alpha. a

When the bearing pin of the assembly 30 is disposed on the seat 100 ofthe opening 90 the bearing pin 40 of the assembly 31 can be disposed onthe seat 111 of the opening 9lto provide a wide or maximum spacingbetween the hooks. Shifting the bearing pin 40 ofthe assembly 31 fromthe seat 111 to the seat 110 of the opening 91 provides a firstintermediate distance between the hooks of the assemblies 30, 31differing from the wide or maximum hook spacing by the distance D-X'.This intermediate position is termed the intermediate-wide position.

When the bearing pin 40 of the assemblies 30 is disposed on the seat 101and the bearing 40 of the assemtion permits increased latitude inoperation of the hoist l r H, during shifting of the assemblies 30, 31as compared with the construction described in reference to FIGS. l-6.

The positions at which the assemblies 30, 31 can be supportedon the beamB are illustrated in FIG. 7 including the wide, narrow," and twointermediate positions. The intermediate positions space the hooks equaldistances apart due to the openings -57 at the ends of the beam being ofthe same size and shape. Although the hook spacing is the same, theintermediate positions provide for the resultant force of the loadsupported by the beam to be exerted at a location on a desired side ofthe center of the beam B.

FIG. 8 illustrates a modified beam B having openings 90, 91 which are ofdifferent configurations to permit the assemblies 30, 31 to be supportedby the beam B at positions which provide four different hook spacings.

bly 31 as disposed on the seat 111 a second intermediate; spacingbetween the hooks of the assembly 30, 31 is provided which differs fromthe maximum spacing by the distance D+X. The second intermediateposition is termed the intermediatemarrow position.

Shifting of the bearing pin 40 of the load supporting assembly 31 to thebearing surface 1 10 provides a narrow or minimum hook spacing betweenthe hooks of the assemblies 30, 31.

- Thus it can be seen that four separate positions of the assemblies 30,31 on the beam 8' can be provided by shifting the assemblies 30, 31between the locations referred to in reference to FIG. 8. It should benoted that the shifting referred to can be accomplished by utilizationof an elevated surface such as the surface 13a referred to inconjunction with FIG. 6.

. While a single embodiment of thepresent invention has been illustratedand described herein and in considerable detail the present invention isnot to be considered to be limited to the precise construction shown. Itis my intention to cover hereby all adaptations modifications and usesof the presentin'vention which come d. a load engaging assemblysuspended from said beam, said assembly including a bearing partengageable with said beam and load-engaging part remote from saidbearing part;

r 1 1 e. said beam including a pair of spaced bearing seats,

a bearing part of said assembly being selectively engageable with one ofthebearing seats of the associated pair of seats; f

f. said beam also including cam means associated with said bearing seatsfor guiding movement of said bearing part betweensaid bearing seats; g.said bearing seats and cam means defined by an opening in said beammember through which said bearing part extends; a first cam portion ofsaid cam means being effective to guide said bearing part from one ofsaid seats toward said other seat in response to down ward movement ofsaid beam relative to said bearing part, said first cam portion guidingsaid bearing I part to a position at which said assembly is unbalancedand exerting a tipping force on said assembly; and,

i. guiding means for constraining said load engaging assembly fortipping movement out of engagement with said first mentioned cam portionand toward said second bearing seat about a tipping axis which extendstransversely of said beam;

j. said guiding means comprising linkage means connected between saidbearing part and said beam member forpreventing skewing of said bearing.cam portions extending upwardly from said bearing seats and convergingproceeding away from said bearing seats, andvwherein the location onsaid first cam portion at which said bearing part of said load engagingmembers tips out of engagement with said first cam portion is spacedsubstantially away from a location on said second cam portion where saidbearing part engages after tipping of said assembly.

4. A crane as defined in claim 3 wherein converging ends of said firstand second cam portions are interconnected by a smoothly curvingconnecting portion of said opening in said beam member, said connectingportion merging with said cam portions at a location spaced verticallyabove said locations on said cam portions whereby said bearing part doesnot contact said connecting portion during shifting between said bearingseats.

5. A crane as defined in claim 1 wherein said linkage means includes alink member connected for rotation with respect to said beam member andfixed against rotation with respect to said bearing part.

6. A crane as defined in claim 5 wherein said connection of said linkmember to said beam member is a pin and slot connection.

7. A crane as defined in claim 5 and further including a second linkmember connected for rotation with respect to said beam member and fixedagainst rotation with respect to said bearing part, said first andsecond link members connected at opposite ends of said bearing part.

8. A crane as defined in claim 1 wherein said opening in said beammember is generally triangular and said cam means further includes asecond cam portion, said cam portions formed by respective sides of saidgenerally triangular opening and said bearing seats defined by thejunctures of a base portion of said triangular opening and thecam'portions, respectively, said base portion of said opening located inspaced relation to said bearing part during movement of said bearingpart between said seats.

9. A crane as defined in claim 8 wherein said cam portions lie in planeswhich converge adjacent an apex of said opening and wherein said camportions are disposed relative to each other so that said bearing partis spaced substantially from said apex at all times during movementbetween said bearing seats.

10. A crane as defined in claim 9 wherein said apex is defined by arecessed portion above the location at which said cam planes converge,said recessed portion including side walls merging with said camportions and a smoothly curving wall connecting said sidewalls.

ll. A'crane as defined in claim 1 wherein said beam defines spaced apartpairs of said bearing seats, the sec- 0nd pair of said seatscooperablewith a bearing part of a second load engaging assembly, saidpairs of bearing seats defined by generally triangular openings in saidbeam and wherein the distance between seats of one pair is greater thanthe distance between seats of said other pair of seats whereby saidbearing parts are en gageable with individual ones of said seats toprovide four different spacings between said load engaging assemblies.

12. An overhead load supporting structure comprising:

a. a hanger beam;

b. a flexible support suspending said beam;

0. a hoist for effecting vertical movement of said beam;

d. a load engaging hook assembly on said beam;

e. said beam including spaced bearing surfaces from which the hookassembly is suspended selectively and one at a time;

f. said hook assembly comprising a bearing part shiftable between saidbearing surfaces and a hook member; I

g. said beam further including structure for exerting a tipping force onsaid hook assembly for tipping said bearing part toward a bearingsurface when said beam is lowered relative to said hook assembly; and,

guiding means for constraining tipping movement of said hookassemblyabout an axis of rotation transverse to the beam and near thebase of said hook assembly as said bearing part is shifting, saidguiding means comprising a base of said hook member which engages ahorizontal surface along a line of contact defining said axis ofrotation.

13. A structure as defined in claim vl2 wherein said hook member isdefined by a plurality of vertically dis posed laminations, laminationsalong sides of said hook member terminating short of said base.

14. A load supporting structure as defined in claim 12 wherein saidguiding means further includes a linkage having a member connected tosaid hanger beam for sliding and rotational motion and nonrotatablyconnected to said bearing part, said linkage preventing skewing of saidbearing part relative to said hanger beam. i

15. A load engaging assembly for connection to a hanger beam comprising:

a. ,a shank adapted to be suspended from said in a vertical Orientation;

b. a load engaging hook-like portiomand,

c. a base of said hook-like portion constructed for touching down on ahorizontal surface'at least at locations spaced apart along a lineextending generally transversely of said hanger beam;

d. said base defining a generally planar surface engageable with thehorizontal surface along said line when the assembly is touched down toprevent said hook from tipping about an axis parallel to said hangerbeam, said line of contact defining an axis about which said loadengaging assembly 'is rotatable.

16. A load supporting device comprising:

a. a movable load supporting structure;

b. a beam suspended from said load supporting structure by flexiblesupporting members;

c. hoist means associated with said supporting members for changing theelevation of said beam; d. a load engaging assembly suspended from saidbeam, said assembly including a bearing part engageable with said beamand load engaging hooklike member remote from said bearing part;

e. said beam including a pair of spaced bearing seats,

a bearing part of said assembly being selectively en- 7 gageable withone of the bearing seats of the associated pair of seats;

f. said beam also including cam means associated with said bearing seatsfor guiding movement of said bearing part between said bearing seats;

g. a first cam portion of said cam means being effective to guide saidbearing part from one of said seats toward said other seat in responseto downward movement of said beam relative to said bearbeam a horizontalsurface along a line of contact during downward movement of said beamrelative to said bearing part, said line of contact extendingtransversely of said beam and defining said tipping axis.

1 7. A load engaging assembly for connection to a hanger beamcomprising:

a.- a shank adapted to be suspended from said beam in a verticalorientation; b. a load engaging hook-like portion; and, c. a base ofsaid hook-like portion constructed for touching down on a horizontalsurface at least at locations spaced apart along a line extendinggenerally transversely of said hanger beam;

' -d. said base and horizontal surface engaging to prevent said hookfrom tipping about an axis to said hanger beam;

. said hook-like portion defined by a plurality of vertically extendinglaminations, laminations along sides of said hook-like portionterminating short of said base whereby the width of the locations onwhich said base touches down is substantially less than the width ofsaid hook-like portion between said sides.

parallel

1. A load supporting device comprising: a. a movable load supportingstructure; b. a beam suspended from said load supporting structure byflexible supporting members; c. hoist means associated with saidsupporting members for changing the elevation of said beam; d. a loadengaging assembly suspended from said beam, said assembly including abearing part engageable with said beam and load engaging part remotefrom said bearing part; e. said beam including a pair of spaced bearingseats, a bearing part of said assembly being selectively engageable withone of the bearing seats of the associated pair of seats; f. said beamalso including cam means associated with said bearing seats for guidingmovement of said bearing part between said bearing seats; g. saidbearing seats and cam means defined by an opening in said beam memberthrough which said bearing part extends; h. a first cam portion of saidcam means being effective to guide said bearing part from one of saidseats toward said other seat in response to downward movement of saidbeam relative to said bearing part, said first cam portion guiding saidbearing part to a position at which said assembly is unbalanced andexerting a tipping force on said assembly; and, i. guiding means forconstrAining said load engaging assembly for tipping movement out ofengagement with said first mentioned cam portion and toward said secondbearing seat about a tipping axis which extends transversely of saidbeam; j. said guiding means comprising linkage means connected betweensaid bearing part and said beam member for preventing skewing of saidbearing part relative to said opening.
 2. A crane as defined in claim 1including a second load engaging assembly suspended from said beam by abearing part and wherein said beam defines spaced pairs of said bearingseats, seats of each pair individually engageable with said bearing partof each of said assemblies.
 3. A crane as defined in claim 1 wherein cammeans includes a second cam portion, said first and second cam portionsextending upwardly from said bearing seats and converging proceedingaway from said bearing seats, and wherein the location on said first camportion at which said bearing part of said load engaging members tipsout of engagement with said first cam portion is spaced substantiallyaway from a location on said second cam portion where said bearing partengages after tipping of said assembly.
 4. A crane as defined in claim 3wherein converging ends of said first and second cam portions areinterconnected by a smoothly curving connecting portion of said openingin said beam member, said connecting portion merging with said camportions at a location spaced vertically above said locations on saidcam portions whereby said bearing part does not contact said connectingportion during shifting between said bearing seats.
 5. A crane asdefined in claim 1 wherein said linkage means includes a link memberconnected for rotation with respect to said beam member and fixedagainst rotation with respect to said bearing part.
 6. A crane asdefined in claim 5 wherein said connection of said link member to saidbeam member is a pin and slot connection.
 7. A crane as defined in claim5 and further including a second link member connected for rotation withrespect to said beam member and fixed against rotation with respect tosaid bearing part, said first and second link members connected atopposite ends of said bearing part.
 8. A crane as defined in claim 1wherein said opening in said beam member is generally triangular andsaid cam means further includes a second cam portion, said cam portionsformed by respective sides of said generally triangular opening and saidbearing seats defined by the junctures of a base portion of saidtriangular opening and the cam portions, respectively, said base portionof said opening located in spaced relation to said bearing part duringmovement of said bearing part between said seats.
 9. A crane as definedin claim 8 wherein said cam portions lie in planes which convergeadjacent an apex of said opening and wherein said cam portions aredisposed relative to each other so that said bearing part is spacedsubstantially from said apex at all times during movement between saidbearing seats.
 10. A crane as defined in claim 9 wherein said apex isdefined by a recessed portion above the location at which said camplanes converge, said recessed portion including side walls merging withsaid cam portions and a smoothly curving wall connecting said sidewalls.
 11. A crane as defined in claim 1 wherein said beam definesspaced apart pairs of said bearing seats, the second pair of said seatscooperable with a bearing part of a second load engaging assembly, saidpairs of bearing seats defined by generally triangular openings in saidbeam and wherein the distance between seats of one pair is greater thanthe distance between seats of said other pair of seats whereby saidbearing parts are engageable with individual ones of said seats toprovide four different spacings between said load engaging assemblies.12. An overhead load supporting structure comprising: a. a hanger beam;b. a flexible support suspending said beam; c. A hoist for effectingvertical movement of said beam; d. a load engaging hook assembly on saidbeam; e. said beam including spaced bearing surfaces from which the hookassembly is suspended selectively and one at a time; f. said hookassembly comprising a bearing part shiftable between said bearingsurfaces and a hook member; g. said beam further including structure forexerting a tipping force on said hook assembly for tipping said bearingpart toward a bearing surface when said beam is lowered relative to saidhook assembly; and, h. guiding means for constraining tipping movementof said hook assembly about an axis of rotation transverse to the beamand near the base of said hook assembly as said bearing part isshifting, said guiding means comprising a base of said hook member whichengages a horizontal surface along a line of contact defining said axisof rotation.
 13. A structure as defined in claim 12 wherein said hookmember is defined by a plurality of vertically disposed laminations,laminations along sides of said hook member terminating short of saidbase.
 14. A load supporting structure as defined in claim 12 whereinsaid guiding means further includes a linkage having a member connectedto said hanger beam for sliding and rotational motion and nonrotatablyconnected to said bearing part, said linkage preventing skewing of saidbearing part relative to said hanger beam.
 15. A load engaging assemblyfor connection to a hanger beam comprising: a. a shank adapted to besuspended from said beam in a vertical orientation; b. a load engaginghook-like portion; and, c. a base of said hook-like portion constructedfor touching down on a horizontal surface at least at locations spacedapart along a line extending generally transversely of said hanger beam;d. said base defining a generally planar surface engageable with thehorizontal surface along said line when the assembly is touched down toprevent said hook from tipping about an axis parallel to said hangerbeam, said line of contact defining an axis about which said loadengaging assembly is rotatable.
 16. A load supporting device comprising:a. a movable load supporting structure; b. a beam suspended from saidload supporting structure by flexible supporting members; c. hoist meansassociated with said supporting members for changing the elevation ofsaid beam; d. a load engaging assembly suspended from said beam, saidassembly including a bearing part engageable with said beam and loadengaging hook-like member remote from said bearing part; e. said beamincluding a pair of spaced bearing seats, a bearing part of saidassembly being selectively engageable with one of the bearing seats ofthe associated pair of seats; f. said beam also including cam meansassociated with said bearing seats for guiding movement of said bearingpart between said bearing seats; g. a first cam portion of said cammeans being effective to guide said bearing part from one of said seatstoward said other seat in response to downward movement of said beamrelative to said bearing part, said first cam portion guiding saidbearing part to a position at which said assembly is unbalanced andexerting a tipping force on said assembly; and, h. guiding means forconstraining said load engaging assembly for tipping movement out ofengagement with said first mentioned cam portion and toward said secondbearing seat about a tipping axis which extends transversely of saidbeam; i. said guiding means comprising a downward facing surface of saidhook-like member engageable with a horizontal surface along a line ofcontact during downward movement of said beam relative to said bearingpart, said line of contact extending transversely of said beam anddefining said tipping axis.
 17. A load engaging assembly for connectionto a hanger beam comprising: a. a shank adapted to be suspended fromsaid beam in a vertical orientation; b. a load engaging hook-likeportion; and, c. a base of said hook-like portion constructed fortouching down on a horizontal surface at least at locations spaced apartalong a line extending generally transversely of said hanger beam; d.said base and horizontal surface engaging to prevent said hook fromtipping about an axis parallel to said hanger beam; e. said hook-likeportion defined by a plurality of vertically extending laminations,laminations along sides of said hook-like portion terminating short ofsaid base whereby the width of the locations on which said base touchesdown is substantially less than the width of said hook-like portionbetween said sides.